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Here Are the Do's and Don'ts of Painting.. Its Nothing Like Painting a House !
So you think your ready to do it your self ?
You're in the paint booth, and you've used compressed air to blow dust from the panels, edges, beneath the moldings and lights, and from the masking paper and the wheel covers ( You do this outside the booth first, then again in the booth with the exhaust fan running, starting furthest away from the fan). You then have washed the vehicle with a Final Wash or Prep Wash (other washes contain silicone which cause fish eyes). You finally wipe the vehicle with a clean tack cloth and you're ready to spray. Occasionally, even after reducing the paint to the manufacturers specifications it may be too dense to spray properly. The usual specs is about 15 seconds in a #4 Ford viscosity cup. Translated into English, that means about 4 seconds to stop dripping off the end of the stir stick. Turn your regulator to about 50 lbs, and get a nice oval pattern. Trigger the gun so that air passes through the cap, but no fluid comes through. Holding the tip of the gun about 8 - 10 inches perpendicular to the surface, start your pass along the panel at a hand speed of about one foot per second and squeeze the trigger to allow fluid. At the edge of the panel, release the trigger to stop fluid but still allow air. This constant air flow ensures that the air is not pulsing with bursts of pressure. This could cause excessive build up at the ends of you pass, leaving runs and sags. Don't stop at the edge of panels either, as this will also cause build up of material. On the back stroke, overlap half the first pass (the edge of the paint should appear dry, and the center wet. This is known as a medium wet coat), triggering the gun as before. Always begin painting furthest away from the exhaust fan, so that you are painting over the over-spray. Otherwise, over-spray will settle onto the painted areas and may not blend in, leaving the surface dry and dull in appearance. With base coats, wait until the coat of paint is DRY before applying the next coat. Otherwise wait until it is almost dry, but a little sticky (the directions are usually close). If you get runs, drips, sags, don't try and fix them while you are painting. You will likely create more problems. They are easy enough to repair after the paint has cured.
Nearly all the materials used in automotive re-finishing are hazardous to your health, the paint especially so. The catalysts usually contain Disincarnate Pre polymer, and it's the that is the main concern. It attacks the central nervous system, and can cause permanent injury. A good air flow, and a fresh air mask should be used. If you don't have any bronchial problems, then an activated charcoal mask can be used. I have used the charcoal mask for years, but now my lungs seem to have an asthmatic reaction to the fumes and I strictly use the fresh air system. Also, some paints contain lead, which may have negative effects on your health when painting or sanding,
Reducers and Thinners:
Aliphatic hydrocarbons (Mineral Spirits- V M P, Naphtha) Aromatic hydrocarbons (Toluene, Xylem) Esters (Ethyl Acetate, Butyl Acetate) Ketone (Acetone, Methyl Ethyl Ketone (MEK)) Various combinations are used along with other additives (retarders, accelerators, and levelers) to reduce the viscosity of the material to a spray-able consistency and accommodate climatic conditions. In general, the smaller the molecular size of the resin (high volume solids), the less reducer will be required. Some products require very little or no reduction. I recommend following the manufacturers directions unless you have extensive experience in spray painting automotive finishes. However, in a pinch, the general rule is that reducers are downward compatible (i.e. you may substitute acrylic enamel reducer for enamel reducer, but NEVER vice versa. The solvents are weaker and you'll end up with an ugly curdled mess in the bottom of the paint gun).
Types of paint:
WHAT TYPE OF PAINTS ARE USED ON AUTOMOBILES ?
Japanese Varnish: In the early years, between 1900 and the 1920's, Japanese varnishes were used. The varnish was applied by brush. Nitrocellulose Lacquer: in the 1920's, several paint manufacturers were involved in the development of nitrocellulose lacquers. This paint had rapid drying and low viscosity properties, and was applied with air pressure through a spray gun leaving a hard dry finish in approximately one hour. When rubbed, polished, and waxed, it far surpassed in durability and appearance the qualities of the Japanese lacquers. Synthetic Enamel: In the mid 1930's, a new and completely different type of paint was developed, the alkyd or synthetic enamels. It proved to have superior qualities in film strength, adhesion, luster, flexibility and durability over all previous paints. The resin base was developed from the reaction between phthalic anhydride and glycerin, with gums, oils and plasticizers added during the manufacturing process a drying oil such as linseed, a polyhydric alcohol, such as glycerine, and a dibasic acid, such as Phthalic Anhydride. It dries by solvent evaporation, like the lacquer paints, but the resin remains soft and sticky when no solvents are present. It cures to a hard finish by absorption of oxygen from the air. The curing process can be accelerated by heat, and several methods of baking enamel were developed. Unlike lacquer, when dry, it needs no polishing to produce a high luster finish. Acrylic Lacquer: As time passed, chemists developed a substitute for nitrocellulose lacquer, using an acrylic resin as a base. The resins used in acrylic lacquer tend to be slightly brittle. This deficiency is overcome by the use of a plasticizer ( a liquid that is a solvent for these resins and softens them slightly). A cellulosic resin is any resin derived from cellulose (pure cotton). Acrylic lacquer was used extensively by General Motors. Acrylic Enamel: During the late 1960's and early 1970's, technology brought on the development of acrylic enamel, which was harder and more durable. Chemically, it is a cousin to synthetic enamel, but is modified with acrylic resin, and is not soft and sticky with no solvents present. It cures further with the absorption of oxygen from the air. Unlike the lacquers, which remain soluble in solvents, the enamel family is insoluble in solvent when cured. An acrylic resin is chemically any polymer whose basic monomers are chemical derivatives of acrylic acid. Polyurethane Enamel: In the mid 1970's, polyurethane enamel was developed to withstand the severe stress of high speed airplane surfaces, which are subject to rapid temperature changes and flexing. This paint was much more durable than the acrylic enamels. Acrylic Urethane Enamel: Acrylic urethane enamels were developed to withstand environmental elements, such as acid rain and ultra violet rays. It is the most durable paint to date.
What Ate Those Extra's Your Adding ?
YOU CAN USE A CATALYST OR HARDENER IN ACRYLIC ENAMEL..
to speed up the curing time of the paint. However, acrylic enamel will cure over time by absorbing oxygen from the atmosphere to complete the molecular cross linking needed to create the polymer. The addition of a catalyst accelerates this process greatly (a few days versus a few months without a catalyst agent). Most catalysts contain isocyanates which can be a health hazard if inhaled. A fresh air supply is strongly recommended. And warning labels are often not as adequate as they should be. Methylenedianiline is used primarily as a chemical intermediate in the closed system production of isocyanates and poly isocyanates and is also a curing agent for epoxy resins and urethane elastomers, a dye intermediate, and a corrosion inhibitor.
Flex Agent:
If you cannot bend the parts easily, you can skip the flex agent. If it is bare plastic, you will have to use plastic prep and plastic primer before painting.
Lacquer Paints:
I don't recommend using lacquer for any reason. It is, the least durable of all the paints made. It does not last long, has no UV resistance, and is not resistant to solvents. And, to make things worse, if you want to repaint over it after you decide its not what you wanted, you have to strip ALL of it off. Every tiny speck. The new urethanes don't agree with it and will blister if there is a small trace of it left on the vehicle. I didn't know it was still sold, since it does not meet any of the new VOC emission rules. But it is in very small quantities. Lacquer is unique, as it does not undergo any molecular changes when it cures. It dries by solvent evaporation alone. The reason for applying several thin coats is that the solvents may become trapped, and the paint may appear dry on the surface, but will be wet underneath. Also, piling on heavy coats may result in checking problems. Nitrocellulose lacquer, or acrylic lacquer will dry to a dull shine (satin). It has to be polished to get a good gloss. Fortunately, although lacquer has many drawbacks, it is very easy to work with. Apply it, wait till it dries thoroughly, and polish it. Its almost the Dummies paint "goof proof".
After The Paint What's Next?
After the paint when it's good and dried (If you used catalyst, I'd wait a couple of days.) now you want to You will need a 7" grinder (something that runs at about 1000-1200 rpm, no faster or you will have many problems. McGuiars #4, #2, #7, #9 compound, a bucket of clean water, a stiff foam sanding block, and some sheets of 8 micron (1500 grit) or 10 micron (2000 grit) wet sandpaper. Do not attempt to polish in direct sunlight. If the paint is non-metallic or clear coated, then wet-sanding is recommended. Do not attempt to sand a metallic paint that has NOT been clear coated as you will disturb the metallic pattern. Wash the car thoroughly. Use 8 micron (1500 grit) or 10 micron (2000) grit wet sandpaper, and fold three or four sheets into three sections so that none of the abrasive sides are touching (from the back, left side in two thirds, right side in one third) and put it into a bucket of CLEAN water. Have a coffee or cold beverage and do nothing for about twenty minutes. This will allow the sandpaper to become soaked and flexible. If you omit this step, you will likely put deep paper cuts into the paint that won't polish out. Use a firm foam sanding block, keep the surface wet and sand the surface, squeezing the water off every once in a while with the sanding block to check for imperfections in the surface. Stay away from edges or high crown lines, as the polishing wheel will burn through these areas very quickly.Once you are satisfied, put a clean wool polishing pad on (if it has old polish on it, then spin the pad and clean it with a dressing tool or something that's clean and not sharp), and apply some #4 McGuiars onto the pad. If you have used 2000 grit to sand the surface with, you might try #2 first. Polish the surface, moving the pad steadily to prevent heat build up (except for lacquer, which can be re-flowed). In a few minutes you will see a good shine develop. Continue with the remaining panels. Put on a foam pad, and use #9 , followed with #7 compound, to bring up a deeper shine and eliminate any swirl marks. Wash off any compound residue when finished and have another cold beverage.
So think your ready to tackle this? Great! Take your time, follow the above advice and DON'T PANIC!! If this is not for you, contact us for a quote. We'll be happy to help you out!
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